Cataract surgery has been the most common surgery in the United States for more than 30 years and its frequency is increasing. A cataract is an opacity of the eye's natural lens which is typically age related. The cataract causes progressively decreased vision along with a progressive decrease in the individual's ability to function in their daily activities. This decrease in function with time can become quite severe. Cataract surgery removes the opaque natural lens and replaces it with a synthetic and clear lens that restores the vision. Synthetic lenses have been very successful at restoring vision for a predetermined focal distance by properly sizing the lens for the individual. However, they have not been able to restore the eye's ability to accommodate.
Accommodation is the eye's ability to change the shape of its natural lens and thereby change its focal distance. This allows an individual to focus on an object at any given distance in their view with an autonomic nervous system feedback response. The person does this automatically, without thinking, by innervating their ciliary body muscle in the eye. The ciliary muscle adjusts radial tension on the natural lens and changes the lens' surface curvatures, and thus adjusts the focal distance of the eye in order that one may focus on a given object.
Without the ability to accommodate, lenses such as reading glasses must be relied upon to focus desired objects. Typically, cataract surgery will leave the individual with a fixed focal distance, usually greater than 20 feet. This allows them to function in activities such as driving without glasses. For activities such as computer work or reading, they need separate glasses.
Several attempts have been made with cataract surgery to restore accommodation in an eye that has lost its ability to change its focal distance. The most successful of these rely upon the insertion of lenses with two to three discrete focal distances. The result with these types of lenses has been only fair, since the designs compromise the overall quality of the vision in exchange for multiple focal distances. Another design alters the position of a fixed focal distance lens by ciliary muscle contraction and thereby changes the overall focal distance of the eye. This design has diminished in popularity, due to poor performance.
A previously disclosed accommodating intraocular lens invented at the University of Arizona (hereinafter “IOL”) utilizes radial tension provided by relaxation of the ciliary muscle to provide an anterior vectored force on the lens thus allowing it to alter the overall lens power without the need to move its position within the eye. The obvious problem is that there must be a posterior vectored force to maintain the lens in a static position within the eye. Furthermore, since this force is tonic and variable, the counter force must be sustainable without migration in the IOL position.
In certain types of haptics, such as ones proposed in U.S. Pat. No. 7,976,520 and U.S. 2008/0300680, the haptics require anchors to puncture or penetrate into the eye wall to support the haptic and keep it in the proper location. This requires a more invasive surgery procedure, which is undesirable.
It is therefore desirable to provide a haptic for supporting the IOL so that it is accommodating and the haptic exerts a sustainable counter force that reduces or prevents migration of the IOL from its proper position, preferably without having to penetrate into eye tissue to support the haptic and keep it in the proper location.